Cantwell Clark

Intraoperative Red Blood Cell Transfusion During Coronary Artery Bypass Graft Surgery Increases the Risk of Postoperative Low-Output Heart Failure

Background— Hemodilutional anemia during cardiopulmonary bypass (CPB) is associated with increased mortality during coronary artery bypass graft (CABG) surgery. The impact of intraoperative red blood cell (RBC) transfusion to treat anemia during surgery is less understood. We examined the relationship between anemia during CPB, RBC transfusion, and risk of low-output heart failure (LOF). Methods and Results— Data were collected on 8004 isolated CABG patients in northern New England between 1996 and 2004. Patients were excluded if they experienced postoperative bleeding or received ≥3 units of transfused RBCs. LOF was defined as need for intraoperative or postoperative intra-aortic balloon pump, return to CPB, or ≥2 inotropes at 48 hours. Having a lower nadir HCT was also associated with an increased risk of developing LOF (adjusted odds ratio, 0.90; 95% CI, 0.82 to 0.92; P=0.016), and that risk was further increased when patients received RBC transfusion. When adjusted for nadir hematocrit, exposure to RBC transfusion was a significant, independent predictor of LOF (adjusted odds ratio, 1.27; 95% CI, 1.00 to 1.61; P=0.047). Conclusions— In this study, we observed that exposure to both hemodilutional anemia and RBC transfusion during surgery are associated with increased risk of LOF, defined as placement of an intraoperative or postoperative intra-aortic balloon pump, return to CPB after initial separation, or treatment with ≥2 inotropes at 48 hours postoperatively, after CABG. The risk of LOF is greater among patients exposed to intraoperative RBCs versus anemia alone.

Gender affects report of pain and function after arthroscopic anterior cruciate ligament reconstruction.

BACKGROUND Gender-related differences in pain have been clearly shown in experimental settings. Clinical studies of such differences have produced conflicting findings. No studies have shown a significant difference in pain experience associated with differences in functional outcomes. Arthroscopic anterior cruciate ligament reconstruction (AACLR) produces pain of moderate intensity and provides a useful setting for examining gender-related differences in pain and function. METHODS This study was a retrospective review of prospectively gathered data collected for a continuous quality improvement program and involved all patients who underwent AACLR at a single outpatient facility since June 1992. Anesthetic, surgical, and perioperative management techniques were standardized. Using a questionnaire, all patients were routinely asked to record pain scores, narcotic consumption, and whether they were able to perform a standardized straight leg-raising maneuver on each of the first 5 postoperative days. RESULTS A total of 736 patients were enrolled for surgery, 58% of whom completed the entire 5-day questionnaire. Women reported higher pain scores at rest as well as with activity on postoperative day 1 compared with men (P < 0.005). In addition, fewer women were able to perform the straight leg-raising maneuver on postoperative day 1 (P = 0.002) and postoperative day 2 (P = 0.004). There was no difference in the amount of narcotics consumed at any time during the study period. CONCLUSIONS Women seem to experience greater intensity of pain after AACLR that is associated with a decrease in an intermediate measure of functional outcome. These differences may result from differences in either response to analgesics or neuroprocessing.

Detection and Elimination of Microemboli Related to Cardiopulmonary Bypass

Background—Neurobehavioral impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass (CPB) are a principal mechanism of cognitive injury. The aim of this work was to study the occurrence of cerebral embolism during CPB and to evaluate the effectiveness of evidence-based CPB circuit component and process changes on the exposure of the patient to emboli. Methods and Results—M-Mode Doppler was used to detect emboli in the inflow and outflow of cardiopulmonary circuit and in the right and left middle cerebral arteries. Doppler signals were merged into a single display to allow real-time associations between discrete clinical techniques and emboli detection. One hundred sixty-nine isolated coronary artery bypass grafting (CABG) patients were studied between 2002 and 2008. There was no statistical difference in median microemboli detected in the inflow of the CPB circuit, (Phase I, 931; Phase II, 1214; Phase III, 1253; Phase IV, 1125; F [3,158]=0.8, P=0.96). Significant changes occurred in median microemboli detected in the outflow of the CPB circuit across phases, (Phase I, 702; Phase II, 572; Phase III, 596; Phase IV, 85; F [3,157]=13.1, P<0.001). Significant changes also occurred in median microemboli detected in the brain across phases, (Phase I, 604; Phase II, 429; Phase III, 407; Phase IV, 138; F [3,153]=14.4, P<0.001). Changes in the cardiopulmonary bypass circuit were associated with an 87.9% (702 versus 85) reduction in median microemboli in the outflow of the CPB circuit (P<0.001), and a 77.2% (604 versus 146) reduction in microemboli in the brain (P<0.001). Conclusions—Changes in CPB techniques and circuit components, including filter size and type of pump, resulted in a reduction in more than 75% of cerebral microemboli.

The association between heart rate and in-hospital mortality after coronary artery bypass graft surgery

Avoidance of tachycardia is a commonly described goal for anesthetic management during coronary artery bypass graft (CABG) surgery. However, an association between increased intraoperative heart rate and mortality has not been described. We conducted an observational study to evaluate the association between preinduction heart rate (heart rate upon arrival to the operating room) and in-hospital mortality during CABG surgery. Data were collected on 5934 CABG patients. Fifteen percent of patients had an increased preinduction heart rate ≥80 bpm. Crude mortality was significantly more frequent among patients with increased preinduction heart rate (Ptrend = 0.002). After adjustment for baseline differences among patients, preinduction heart rate ≥80 bpm remained associated with increased mortality (Ptrend < 0.001). The increased heart rate may be a cause of the observed mortality. Alternatively, faster heart rate may be either a marker of patients with irreversible myocardial damage, or a marker of patients with limited cardiac reserve at risk for further injury. Lastly, faster heart rate may be a marker for under-use of &bgr;-adrenergic blockade. Because the use of preoperative &bgr;-adrenergic blockade in CABG patients is associated with improved in-hospital survival, further investigation concerning the effect of intraoperative treatment of increased heart rate with &bgr;-adrenergic blockers on mortality after CABG surgery is warranted.

Experience with 724 epidurograms for epidural catheter placement in pediatric anesthesia.

Introduction: Epidural analgesia via continuous catheters, placed either via the caudal approach or directly at the desired level, is a commonly used technique in children. It is particularly important that these catheters are placed correctly because most are placed under general anesthesia and require deep sedation or repeat general anesthesia for replacement if malfunctioning. Ideally, correct placement should be confirmed at the time of insertion. Methods: We combined the experience of 2 academic teaching hospitals that both perform routine epidurography for the placement of epidural catheters in children. The data from 2 quality assurance regional anesthesia databases were screened for unrecognized misplacements of epidural catheters. Results: Of a total of 724 epidurograms, 45.8% were caudal catheters, 9.6% were lumbar catheters, and 32.3% were thoracic catheters. Epidurograms detected 12 (1.6%) unexpected misplacements: 4 were intrathecal, 3 were intravenous, and 3 were intraperitoneal. Conclusions: Our experiments suggest that confirmation of epidural catheter placement via epidurogram is highly efficacious. Epidurography is the only currently available technique that accomplishes all of the following: (a) confirms correct placement, (b) rules out incorrect anatomic space, and (c) predicts analgesic coverage.

Repair of hypoplastic left heart syndrome of a 4.25-kg Jehovah’s witness

The care of patients who refuse homologous transfusions has challenged cardiac surgery teams to refine blood conservation techniques and question standard trans-fusion practices. We cared for a newborn child with hypoplastic left heart syndrome (HLHS) whose parents refused to give consent to care for the child that involved the transfusion of homologous blood. A Norwood Stage I procedure was planned with the understanding that transfusions would be avoided, if possible. A court order was obtained that specified the conditions under which the attending physicians would transfuse the newborn. The birth weight of the patient was 4.25 kg. A low prime cardiopulmonary bypass (CPB) circuit and aggressive blood conservation techniques that included modified ultrafiltration (MUF) allowed the completion of the repair and CPB portion of the operation without the use of blood. The lowest hematocrit during CPB was 20%. After an unsuccessful attempt to separate from CPB, blood was transfused. Recovery was consistent for HLHS patients following Norwood Stage I. However, at 1 month postoperatively, the patient did require a shunt reduction for pulmonary overcirculation. Norwood Stage II repair was completed at age 4 months without donor blood. The key to a successful outcome is a well-thoughtout plan by the surgeon, anesthesiologist and perfusionist. This plan should include careful monitoring of the patient’s oxygenation and cardiovascular status.

A model for cardiopulmonary bypass redesign

Introduction: A portion of patients undergoing cardiac surgery may develop focal and/or subtle brain injuries secondary to cardiac surgery. There is evidence that, in some cases, these injuries may be related to cardiopulmonary bypass (CPB). Embolism and hypoperfusion are the dominant mechanisms for focal neurologic injuries among coronary artery bypass graft (CABG) surgery patients. Recent studies suggest that these mechanisms may also produce the more prevalent subtle neurological deficits. The aim of our current work is to obtain a thorough understanding of the processes of care associated with the production of embolic activity, cerebral hypoperfusion, and hemodynamic aberrations that often occur during CPB. Methods: We developed a system for simultaneous recording of physiologic parameters, embolic activity in the CPB circuit and in the cerebral arteries, and near infrared regional cerebral oxyhemoglobin saturation (NIRS) during cardiac surgery. All data were synchronized with a video recording of the surgical procedure. Periods of embolic activity and NIRS were subsequently related to surgical and CPB processes of care through a systematic review of the patient’s surgical case video. Results: To date, we have enrolled 47 patients undergoing coronary and/or valvular procedures. We have observed wide variation across patients in detected cerebral embolic counts, NIRS and physiologic parameters. We have identified increased embolic counts in the CPB circuit related to specific processes and events such as the method of venous drainage, the entrainment of air in the venous line, the injection of medications into the CPB circuit and blood sampling from the CPB circuit. A portion of detected changes in NIRS were related to periods of hypotension and positioning of the heart during the construction of distal coronary artery grafts on the posterior coronary artery vessels. Summary: Use of this model provides the surgical team with detailed information regarding the contribution of CPB to the creation of precursors of neurological injury. This system provides meaningful data to guide the surgical team in the redesign of the CPB system and associated techniques.

A Method for Identifying Mechanisms of Neurologic Injury from Cardiac Surgery

BACKGROUND A method for linking discrete surgical and perfusion-related processes of care with cerebral emboli, cerebral oxyhemoglobin desaturation, and hemodynamic changes may offer opportunities for reducing overall neurologic injury for patients undergoing cardiac surgery. METHODS An intensive intraoperative neurologic and physiologic monitoring approach was developed and implemented. Mechanisms likely to produce embolic (cerebral emboli), hypoperfusion (oxyhemoglobin desaturation), and hypotensive (hemodynamic changes) neurologic injuries were monitored and synchronized with the occurrence of surgical and perfusion clinical events/techniques using a case video. RESULTS The system was tested among 32 cardiac surgery patients. Emboli were measured in the cerebral arteries and outflow of the cardiopulmonary bypass circuit among nearly 75% and 85% of patients, respectively. Oxyhemoglobin desaturation was measured among nearly 70% of patients. Hemodynamic information was recorded in 100% of patients. CONCLUSIONS We developed and successfully implemented a method for detailed real-time associations between processes of clinical care and precursors of neurologic injury. Knowledge of this linkage will result in the redesign of clinical care to reduce a patients risk of neurologic injury.